ExecuteScalar() method

[tester321]

hi i having trouble with ExecuteScalar(),

[1]I getting a null reference exception that was un handled by me.

[2] use the keyword 'new' to create an object instance, but when i add new i get:
Object reference not set to an instance of an object.

Here are some lines of code, any suggestions, thanks:

Command.Parameters.Add("@pass", SqlDbType.NVarChar).Value = strPassword;

connection.Open();

int va1 = (int)Command.ExecuteScalar();

Console.WriteLine(va1);

connection.Close();

 

[phinoppix]

Hi,
I'm not sure I understand your question, but I will just like to make a comment on your sample code. It is unsafe to do an immediate cast against ExecuteScalar(). Instead, store the value on an object type var and test it. There are 3 conditions to watch: 1) no record returned, 2) a record is returned but the value is a NULL, 3) data received.

[COLOR=green]/* Configure command object */[/color]
SqlConnection con = ...;
SqlCommand cmd = ...;

con.Open();
object data = cmd.ExecuteScalar();
con.Close();

if (data == null)
	MessageBox.Show("No record received.");
else if (data is DBNull)
	MessageBox.Show("Record received. Value is DBNull.");
else
	MessageBox.Show("Data received = " + data.ToString());

hope this helps

 

[tester321]

phinoppix, thank for the pointers, i'm having problems showing the message, the code is in LoginForm.acsx.cs

and i'm including the LoginForm into a page called memberLogin, like so:

<%@ Register Src="userControls/LoginForm.ascx" TagName="LoginForm" TagPrefix="uc1" %>

And its in the memberLogin.aspx page i have a place holder for msg

if (data == null)
     Msg.Txt("No record received.");
else if (data is DBNull)
     Msg.Txt("Record received. Value is DBNull.");
else
     Msg.Txt("Data received = " + data.ToString());

Msg does not exist in the current context, intellisense gave me the option of:
WebApplication1.member_area.MemberLogin.Msg.txt...

but still not referenced correctly? any suggestions, thanks

 

[AlexCuse]

Not sure what you're trying to do, but why not use Response.Write to show the messages?

If you want to have a message box, here is a function I use in a separate class to put message boxes on my page.

    public static void CreateMsgBox(System.Web.UI.Page aspxPage, string strMessage, string strKey)
    {
        string strScript = "<script language = JavaScript>alert('" + strMessage + "')</script>";
        if (!aspxPage.ClientScript.IsStartupScriptRegistered(strKey))
        {
            aspxPage.ClientScript.RegisterStartupScript(aspxPage.GetType(), strKey, strScript);
        }
    }

Hope it helps,

Alex

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